Printable reflective features formed from multiple inks and processes for making them

ABSTRACT

The invention relates to reflective features formed from multiple inks. In one embodiment, the reflective feature comprises a substrate having a first region and a second region, the first and second regions having different surface characteristics; a first reflective element disposed on the first region; and a second reflective element disposed on the second region, wherein the first reflective element is more adherent than the second reflective element to the first region. In another embodiment, the reflective feature comprises multiple layers formed from different inks exhibiting enhanced reflectivity and/or durability. The invention is also to processes for forming these features, preferably through a direct write printing process.

FIELD OF THE INVENTION

The present invention relates to reflective features and to processesfor making reflective features. In particular, the invention relates toreflective features formed on substrates having regions with differentsurface characteristics, to multi-layered features having highreflectivity and durability, and to processes for making such features.

BACKGROUND OF THE INVENTION

Recent advances in color copying and printing have put increasingimportance on developing new methods to prevent forgery of securitydocuments such as banknotes. While there have been many techniquesdeveloped, one area of increasing interest is in developing reflectivefeatures that cannot be readily reproduced, particularly by a colorcopier or printer.

One approach that has been taken is to formulate an ink for creating aprinted image that is visually distinct from its reproduction. Forexample, U.S. Pat. Nos. 5,059,245, 5,569,535, and 4,434,010, theentireties of which are incorporated herein by reference, describe theuse of stacked thin film platelets or flakes. Images produced with thesepigments exhibit angular metamerism. These pigments have beenincorporated into security inks used, for example, in paper currency.These pigments have also been incorporated into plastics applications(see, for example, PCT Publication WO 00/24580, published May 4, 2000).Additional inks and reflective features are described in U.S. Pat. Nos.4,705,356; 4,779,898; 5,278,590; 5,766,738; and 6,114,018, theentireties of which are incorporated herein by reference.

Another approach used to produce security documents has been to producea “covert” image that contains a material which cannot be seen by thenaked eye but which can be made visible under specific conditions. Forexample, U.S. Pat. Nos. 5,324,567, 5,718,754, and 5,853,464 disclose theuse of Raman active compounds. U.S. Pat. Nos. 5,944,881 and 5,980,593describe fluorescent materials that can be used in an ink. Also, U.S.Pat. No. 4,504,084 discloses a document containing an informationmarking comprised of a first color that is at least partially opaque orvisible in infrared light and a second color, which conceals the firstcolor in the visible spectrum, but is invisible to infrared light.

While these efforts afford printed images that are difficult toreproduce, advances in color copiers and color printers continue to bemade. Therefore, the need exists for new highly secure features and formethods for producing such features, particularly for securitydocuments, which features cannot be easily reproduced, and which arevisually distinct from their reproductions.

Additionally, the need exists for providing the ability to createreflective features that display variable information, e.g., informationthat is individualized for a specific product unit, such as a serialnumber, which variable information cannot be easily or readilyduplicated or copied.

The need also exists for reflective features that are highly reflective.Highly reflective features, particularly reflective features thatdisplay variable information, are generally more difficult to reproducethan non-reflective features.

The need also exists for highly durable reflective features that canwithstand the rigors of use, for example, the extensive handlinginvolved with widespread circulation, or the repeated washing to whichauthenticated garments may be subject.

SUMMARY OF THE INVENTION

In a first embodiment, the invention is to a reflective feature,comprising: (a) a substrate having a first region and a second region,the first and second regions having different surface characteristics;(b) a first reflective element, preferably comprising metallicnanoparticles, disposed on the first region; and (c) a second reflectiveelement, preferably comprising metallic nanoparticles, disposed on thesecond region, wherein the first reflective element is more adherentthan the second reflective element to the first region. Preferably, thesecond reflective element is more adherent than the first reflectiveelement to the second region.

Optionally, the first reflective element is disposed exclusively on thefirst region. The substrate may further comprise a third region, and thereflective feature further comprises a third reflective element disposedon the third region, wherein the third reflective element is moreadherent than the first reflective element or the second reflectiveelement to the third region.

The first region and/or the second region optionally comprises acomposition selected from the group consisting of foil, film, UV-coatedlacquer, paper, coated paper, polymer, and printed paper.

The first reflective element and the second reflective elementoptionally form a continuous graphical feature that spans at least apart of the first region and at least a part of the second region.

In a preferred embodiment, at least one of the first reflective elementand/or the second reflective element comprises variable information.

The substrate optionally is selected from the group consisting of abanknote, a brand authentication tag, a tax stamp, an ID document, analcoholic bottle, and a tobacco product.

In one embodiment, the first region comprises a first undercoat. In thisembodiment, the first reflective element optionally exhibits enhancedreflectivity relative to the reflectivity of the first reflectiveelement on the first region in the absence of the first undercoat.Additionally, the second region optionally comprises a second undercoat.In this embodiment, the second reflective element optionally exhibitsenhanced reflectivity relative to the reflectivity of the secondreflective element on the second region in the absence of the secondundercoat.

In one embodiment, the feature further comprises a first overcoatdisposed on the first reflective element. In this embodiment, the firstreflective element optionally exhibits enhanced reflectivity relative tothe reflectivity of the first reflective element without the firstovercoat. Also, in this embodiment, the first reflective elementoptionally exhibits enhanced durability relative to the durability ofthe first reflective element without the first overcoat. The firstovercoat may further be disposed on the second reflective element. Inthis embodiment, the second reflective element optionally exhibitsenhanced reflectivity relative to the reflectivity of the secondreflective element without the first overcoat. Also, in this embodiment,the second reflective element optionally exhibits enhanced durabilityrelative to the durability of the second reflective element without thefirst overcoat. In another aspect, the feature further comprises asecond overcoat disposed on the second reflective element, wherein thesecond reflective element optionally exhibits enhanced reflectivityrelative to the reflectivity of the second reflective element withoutthe second overcoat. Also, in this embodiment, the second reflectiveelement optionally exhibits enhanced durability relative to thedurability of the second reflective element without the second overcoat.

Optionally, the first region is more or less porous than the secondregion. In another embodiment, the first region is more or lesshydrophobic than the second region.

In another embodiment, the present invention is directed to a processfor forming a reflective feature, the process comprising the steps of:(a) providing a substrate comprising a first region and a second region;(b) direct write printing, e.g., piezo-electric, thermal,drop-on-demand, or continuous ink jet printing, a first ink onto thefirst region to form a first reflective element; and (c) direct writeprinting a second ink onto the second region to form a second reflectiveelement, wherein the first ink is more adherent than the second ink tothe first region. Preferably, the second ink is more adherent than thefirst ink to the second region. At least one of the first ink and thesecond ink preferably comprises metallic nanoparticles. This process maybe employed, for example, to form the above-described reflectivefeature.

Optionally, the process further comprises the step of direct writeprinting a third ink onto a third substrate surface to form a thirdreflective element, wherein the substrate further comprises the thirdsubstrate surface, and wherein the third ink is more adherent than thefirst ink or the second ink to the third region.

In another embodiment, the invention is to a reflective feature,comprising: (a) a substrate having a first surface; (b) a first coatingdisposed on the first surface and having a second surface; and (c) areflective element having a third surface and comprising nanoparticlesdisposed, at least in part, on the second surface.

Optionally, the feature further comprises a second coating, whichoptionally is transparent, having a fourth surface disposed, at least inpart, on the third surface. The second coating optionally comprises amaterial selected from the group consisting of: a varnish, an offsetvarnish, a dry offset varnish, a shellac, latex, and a polymer.

In this embodiment, the first surface optionally comprises two regionshaving different surface characteristics, and the first coating coversat least a portion of both regions, and the reflective elementoptionally covers at least a portion of the two regions.

Optionally, the first coating comprises a material selected from thegroup consisting of varnishes, offset varnishes, dry offset varnishes,shellacs, and polymers. In one aspect, the first coating furthercomprises a colorant.

The nanoparticles optionally comprise phosphorescent nanoparticles. Inanother embodiment, the nanoparticles comprise metallic nanoparticles.In this embodiment, a majority of the metallic nanoparticles optionallyare necked with at least one adjacent metallic nanoparticle. Themetallic nanoparticles optionally comprise a metal selected from thegroup consisting of silver, gold, zinc, tin, copper, platinum andpalladium, and alloys thereof. The metallic nanoparticles may have anaverage particle size of less than about 200 nm, e.g., an averageparticle size of from about 50 nm to about 100 nm.

The reflective element optionally comprises a reflective layer that isat least partially semitransparent. The reflective element optionallycomprises a continuous reflective layer or a non-continuous reflectivelayer. Preferably, the reflective feature is more reflective than itwould be in the absence of the first coating.

In one aspect, at least one of the first surface or the second surfacehas an image disposed thereon, and at least a portion of the image isviewable through the reflective element when viewed at a first anglerelative to the third surface, and the least a portion of the image isat least partially obscured when viewed from a second angle relative tothe third surface. The second angle may, for example, be about 180°minus the angle of incident light, relative to the third surface. Theimage optionally is formed from a printing process selected from thegroup consisting of direct write printing, intaglio printing, gravureprinting, lithographic printing and flexographic printing processes. Theimage may be selected from the group consisting of a hologram, a blackand white image, a color image, a watermark, a UV fluorescent image,text and a serial number.

In one embodiment, the reflective element comprises a plurality ofreflective images. Optionally, the reflective element comprises aplurality of reflective microimages, wherein the plurality of reflectivemicroimages has an average largest dimension of less than about 0.5 mm.At least one microimage optionally comprises variable data.

In another embodiment, the invention is to a process for forming areflective feature, the process comprising the steps of: (a) providing asubstrate having a first surface; (b) forming a first coating on thefirst surface, the first coating having a second surface; and (c)forming a reflective element on the second surface, the reflectiveelement having a third surface and comprising nanoparticles. Thisprocess may be employed, for example, to form the above-describedmulti-layer reflective feature.

In this embodiment, the first surface optionally comprises two regionshaving different surface characteristics, and the first coating coversat least a portion of both regions, and reflective element optionallycovers at least a portion of the two regions. Step (b) optionallycomprises depositing a first ink onto the first surface and treating thedeposited first ink under conditions effective to form the firstcoating. The depositing preferably comprises direct write printing thefirst ink onto the first surface. The treating optionally comprises oneor more of: drying the deposited first ink, heating the deposited firstink, and/or applying UV radiation to the deposited first ink. Step (c)optionally comprises depositing a second ink onto the second surface andtreating the deposited second ink under conditions effective to form thereflective element, wherein the depositing optionally comprises directwrite printing the second ink onto the second surface, and the treatingoptionally comprises one or more of: drying the deposited second ink,heating the deposited second ink, and/or applying UV radiation to thedeposited second ink. Optionally, the process further comprises the stepof: (d) forming a second coating on the third surface, the secondcoating having a fourth surface. The second coating optionally istransparent.

In another embodiment, the invention is to a reflective feature,comprising (a) a substrate; (b) a reflective element comprising metallicnanoparticles; and (c) an overcoat comprising a colorant. The overcoatoptionally is transparent. The overcoat optionally comprises a materialselected from the group consisting of: a varnish, an offset varnish, adry offset varnish, a shellac, latex, and a polymer.

In another embodiment, the invention is to a process for forming areflective feature, the process comprising the steps of: (a) providing asubstrate; (b) forming a reflective element on the substrate, thereflective element comprising metallic nanoparticles; and (c) forming anovercoat on the reflective element, the overcoat comprising a colorant.In this embodiment, the step of forming the reflective elementcomprising metallic nanoparticles optionally comprises direct writeprinting an ink comprising the metallic nanoparticles onto thesubstrate. The step of forming the overcoat comprising a colorantoptionally comprises direct write printing an ink comprising thecolorant onto the substrate and/or the reflective element.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood in view of the appendednon-limiting figures, wherein:

FIG. 1 illustrates a reflective feature disposed on a substrate having afirst region and a second region, the first and second regions havingdifferent surface characteristics;

FIG. 2 illustrates another substrate having a first region and a secondregion, the first and second regions having different surfacecharacteristics;

FIG. 3 illustrates a reflective feature disposed on a substrate having afirst region and a second region, the first and second regions havingdifferent surface characteristics, and the feature extending across theinterface between the two regions;

FIG. 4 illustrates an intermediate reflective feature disposed on thefirst region of a substrate having a first region and a second region,the first and second regions having different surface characteristics;

FIG. 5 illustrates a wetting ink droplet on a substrate surface;

FIG. 6 illustrates a non-wetting ink droplet on a substrate surface;

FIG. 7 illustrates an exploded view of a multi-layered feature accordingto another embodiment of the present invention; and

FIG. 8 illustrates a non-exploded view of the feature of FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION Introduction

The present invention, in one embodiment, relates to a reflectivefeature, preferably a reflective security feature or a reflectivedecorative feature, formed by printing multiple inks onto multipleregions of a substrate, the regions having different surfacecharacteristics from one another. The reflective feature includes afirst reflective element disposed on a first region and a secondreflective element disposed on a second region, wherein the firstreflective element is more adherent than the second reflective elementto the first region. The second reflective element preferably issimilarly more adherent than the first reflective element to the secondregion. As it is generally difficult to form features on a substratehaving multiple regions with different surface characteristics, thisembodiment of the invention provides a highly securedifficult-to-reproduce reflective feature having significant commercialvalue. The invention also relates to processes for forming suchreflective features.

In another embodiment, the invention relates to a multi-layeredreflective feature, preferably a reflective security feature or areflective decorative feature, formed from multiple inks. Themulti-layered reflective features desirably are highly durable and/orhighly reflective. The invention also relates to processes for formingsuch reflective features.

As used herein, the term “security feature” means a feature that isplaced on or otherwise incorporated into an article (e.g., a tag orlabel, a document such as a passport, check, bond, banknote, currency,ticket, etc.), directly or indirectly, for the purpose of authenticatingthe article. As used herein, the term “decorative feature” means afeature that is not provided primarily for an authentication purpose,but rather primarily for a graphical or decorative purpose. As usedherein the term “reflective element” means a reflective portion of areflective feature.

Possible uses for the reflective features of the present invention mayvary widely. Generally, the reflective features of the invention may beemployed as security features in any product that is subject tocounterfeiting, imitation or copying. Thus, in one embodiment, theinvention is to a banknote comprising the reflective feature of thepresent invention. In another embodiment, the invention is to afiduciary document comprising the reflective feature of the invention.In another embodiment, the invention is to a certificate of authenticitycomprising the reflective feature of the invention. In anotherembodiment, the invention is to a brand authentication tag comprisingthe reflective feature of the present invention. In another embodiment,the invention is to an article of manufacture comprising a brandauthentication tag comprising the reflective feature of the presentinvention. In another embodiment, the invention is to a tax stampcomprising the reflective feature of the present invention. In anotherembodiment, the invention is to an alcohol bottle comprising a tax stampcomprising the reflective feature of the present invention. In anotherembodiment, the invention is to a tobacco product container comprising atax stamp comprising the reflective feature of the present invention.The present invention is not limited to the foregoing examples, and anumber of other substrates and/or substrate surfaces may comprise thereflective features of the present invention.

The reflective features of the present invention are not limited tosecurity applications. The features may also be employed, for example,for brand protection, brand personalization (e.g., short run personalcare/cosmetics), trademarks, or in graphics, decorative features,non-secure documents (e.g., business cards, greeting cards, paperproducts, etc.), advertisements, mass mailings, wall paper, ceramictiles, to name but a few. Thus, in one embodiment, the reflectivefeature comprises a decorative feature. The present invention is notlimited to the foregoing examples, and a number of other substratesand/or substrate surfaces may comprise the features of the presentinvention.

Reflective Features Formed on Regions of a Substrate Having DifferentSurface Characteristics

In a first embodiment, the invention is to a reflective feature,preferably a reflective security feature or a reflective decorativefeature, comprising a substrate having a first region and a secondregion, the first and second regions having different surfacecharacteristics. A first reflective element is disposed on the firstregion and a second reflective element is disposed on the second region.In this embodiment, the first reflective element is more adherent thanthe second reflective element to the first region, and, preferably, thesecond reflective features is more adherent than the first reflectiveelement to the second region.

As used herein, the term “surface characteristic” is meant to refer toany property that affects the level of adherence of a substance, e.g., afluid ink or a composition formed therefrom, to a surface. By way ofnon-limiting examples, wetting characteristics, porosity, surfaceenergy, charge, bonding ability and hydrophobicity are surfacecharacteristics that may affect the level of adherence of a substance toa surface. In one embodiment, for example, the first region (and thefirst surface thereof) is more porous than the second region (and thesecond surface thereof). In another embodiment, the first region (andthe first surface thereof) is less porous than the second region (andthe second surface thereof). In another embodiment, the first region(and the first surface thereof) is more hydrophilic (less hydrophobic)than the second region (and the second surface thereof). In anotherembodiment, the first region (and the first surface thereof) is lesshydrophilic (more hydrophobic) than the second region (and the secondsurface thereof). In another embodiment, the first region (and the firstsurface thereof) has a surface energy that is greater than the surfaceenergy of the second region (and the second surface thereof). In anotherembodiment, the first region (and the first surface thereof) has asurface energy that is less than the surface energy of the second region(and the second surface thereof).

For purposes of the present specification, the level of adherence of thefirst and second reflective elements to the first and second regions maybe determined by ASTM rub test: ASTM D-5264D92, the entirety of which isincorporated herein by reference, wherein the adherence is rated on ascale of 1 to 5, a rating of 5 indicating the highest level ofadherence. Under this test, the first reflective element preferably hasan adherence to the first region that is rated a 2 or greater, 3 orgreater, 4 or greater or 5 on ASTM D-5264D92. Additionally, the secondreflective element preferably has level of adherence to the secondregion that is 2 or greater, 3 or greater, 4 or greater or 5 asdetermined by ASTM D-5264D92. In another aspect, the durability of thefirst and second reflective elements may be determined by using a Scotchtape test, in which pressure-sensitive tape is applied to an area of thefeature (e.g., the first and second reflective elements thereof), whichoptionally is cross-hatched with scratched lines, and then lifted off.Adhesion is considered to be adequate if the coating is not pulled offby the tape when it is removed. Substantial removal of the first and/orsecond reflective elements with the Scotch tape indicates durabilityfailure under this test.

The specific form of the reflective feature, e.g., reflective securityfeatures or reflective decorative features, has myriad possibilities. Ina preferred embodiment, the reflective feature comprises an image. Theimage may vary widely, but may include, for example, a geometric imageor shape, alphanumeric characters, microimages, microprint (2 pt fontsize or smaller, height less than about 400 μm, e.g., less than about300 μm, less than about 200 μm or less than about 100 μm), a personalimage (e.g., image of an individual), photograph, fingerprint, design,barcode, logo, trademark, pattern, e.g., guilloche pattern or rosettepattern, or other object. In a preferred embodiment, the reflectivefeatures exhibit variable information, as discussed in greater detailbelow.

In a preferred embodiment, the first reflective element (as well as thefirst ink used to form the first reflective element) is disposedexclusively on the first region. As the second reflective element isoptionally more adherent than the first reflective element to the secondregion, this embodiment minimizes the potential for beading, smearing,over-saturation and/or overall poor adhesion that would likely occur ifthe first reflective element (or a portion thereof) were formed on thesecond region. Forming the first reflective element exclusively on thefirst region, therefore, contributes to the desired reflectivity and/orappearance of the overall reflective feature.

Similarly, in a preferred embodiment, the second reflective element (aswell as the second ink used to form the second reflective element) isdisposed exclusively on the second region. As the first reflectiveelement is more adherent than the second reflective element to thesecond region, this embodiment minimizes the potential for beading,smearing, over-saturation and/or overall poor adhesion that would likelyoccur if the second reflective element (or a portion thereof) wereformed on the first region. Disposing the second reflective elementexclusively on the second region, therefore, contributes to the desiredreflectivity and/or desired appearance of the overall reflectivefeature.

The reflective features of the invention, e.g., reflective securityfeatures or reflective decorative features, are not limited to beingformed on substrates having two regions (e.g., two surfaces) withdifferent surface characteristics. In one embodiment, the substratefurther comprises a third region, the reflective feature furthercomprising a third reflective element disposed on the third region,wherein the third reflective element (as well as the ink used to formthe third reflective element) is more adherent than the first reflectiveelement or the second reflective element to the third region. Thepresence of a third reflective element disposed on a third regionimproves the ability to reliably authenticate an item such as, e.g., abanknote if such an item comprises a substrate comprising a firstregion, a second region, and a third region. As discussed below, theability to form reflective elements on different substrate surfaces,while maintaining a uniform overall appearance of the reflective featureamong the reflective elements, is a particularly useful aspect of thepresent invention, as it is difficult to reproduce such reflectivefeatures. Of course, substrates having more than three regions may alsobe employed.

In one embodiment, the first reflective element and/or the secondreflective element are specularly reflective or mirror-like. Specularlyreflective elements in general are desirable because they are readilyidentifiable, yet generally difficult to form and, therefore, toreproduce, for example, even with a sophisticated color photocopier.Preferably, the reflective feature of the present invention comprises afirst reflective element comprising metallic nanoparticles. Additionallyor alternatively, the second reflective element comprises metallicnanoparticles. The use of metallic nanoparticles to form the firstand/or second reflective features is also desirable in that inkscomprising metallic nanoparticles may be deposited using direct writeprinting processes, e.g., ink jet printing, to form the reflectiveelements, and in particular, to form reflective features comprisingvariable information, as discussed below. Further, metallicnanoparticles have been found to impart highly reflective properties tothe reflective features. Thus, this embodiment provides two aspects thatare difficult to reproduce and, therefore, can function to verify theauthenticity of an item. The first aspect that is difficult to reproduceis forming a reflective feature disposed on different regions of asubstrate having different surface characteristics. The second aspectthat is difficult to reproduce is the highly reflective nature ofreflective elements comprising metallic nanoparticles.

The reflective features, e.g., reflective security features orreflective decorative features, preferably comprise metallicnanoparticles. If present, the nanoparticles optionally are in the formof a continuous reflective film, which may be formed through removal ofthe liquid phase, e.g., ink vehicle, and/or through post-depositiontreating, e.g., curing. If the reflective features comprise metallicnanoparticles, a majority (e.g., at least 50%, at least 70%, at least85% or at least 95%) of the metallic nanoparticles optionally are neckedwith at least one adjacent metallic nanoparticle in the continuous film.By necking it is meant that adjacent particles are physically connectedto one another through a necking region, while retaining at least somerecognizable degree of their original, e.g., spherical, form. The degreeof necking will vary widely depending, for example, on the composition(and melting point) of the nanoparticles and on the treating, e.g.,curing, conditions employed in forming the reflective features. Inanother embodiment, a majority (e.g., at least 50%, at least 70%, atleast 85% or at least 95%) of the metallic nanoparticles are independentfrom (meaning not necked with) any adjacent nanoparticles in thecontinuous film.

In one embodiment, the reflective feature, is disposed, e.g.,positioned, formed or printed, over an underlying element (e.g., anunderlying image, optionally an underlying reflective image), theunderlying element preferably being at least partially visible throughthe feature when viewed at one angle (for example, if the reflectivefeature is translucent or has gaps in it through which one can view theunderlying element). The underlying element may become obscured,however, when viewed from another angle, relative to the surface of thereflective feature. The effect of obscuring an underlying element isfurther described in co-pending U.S. patent application Ser. No.11/331,233, filed Jan. 13, 2006, entitled “Reflective features, TheirUse and Processes for Making Them,” the entirety of which isincorporated herein by reference. Optionally, the underlying elementcomprises metallic particles, e.g., metallic nanoparticles.

In another embodiment, an overlying element (e.g., an overlying image,optionally an overlying reflective image) is disposed over, e.g., on topof, the first and/or second reflective elements. Optionally, theoverlying element is clearly visible when viewed from one angle (a firstangle) and the overlying reflective element is at least partiallyobscured when viewed from another angle (a second angle). Optionally,the overlying element comprises metallic particles, e.g., metallicnanoparticles.

In one embodiment of the present invention, the first reflective elementand the second reflective element form a continuous graphical featurethat spans at least a part of the first region and at least a part ofthe second region. As used herein, the term “graphical feature” is meantto refer to the overall shape or outline of the reflective feature. Asuse herein, the term “continuous” is meant to refer to a single,discreet, connected object or part of an object, optionally formed fromone or more inks, substantially free of gaps. Non-limiting examples ofgraphical features of the present invention include any geometric imageor shape, one or more alphanumeric characters, microimages, microprint(2 pt font size or smaller, height less than about 400 μm, e.g., lessthan about 300 μm, less than about 200 μm or less than about 100 μm),personal image (e.g., image of an individual), photograph, fingerprint,design, barcode, logo, trademark, pattern, e.g., guilloche pattern orrosette pattern, or other object. Additionally, the first reflectiveelement and the second reflective element optionally form a continuousgraphical feature that extends across the interface between the firstregion and the second region of a substrate to form a continuousgraphical feature that is difficult to reproduce, and may serve toauthenticate an item. FIG. 3, discussed below, provides an example of acontinuous graphical feature in which the letter “A” extendscontinuously across the interface 11 between first region 12 and secondregion 13. This embodiment is particularly desirable for securityapplications if the first and second regions exhibit substantiallydifferent surface characteristics, as it is difficult to form acontinuous graphical feature, having a single uniform appearance,extending across regions having substantially different surfacecharacteristics. FIGS. 1 and 2, discussed below, provide examples ofnon-continuous graphical reflective feature having a first reflectiveelement 7 comprising the numbers “01,” and a second reflective element 8comprising the numbers “234,” the second reflective element 8 beingseparate from the first reflective element 7, but forming a singlegraphical reflective feature.

The substrate, as well as the compositions forming the first and secondregions thereof, may vary widely. In one embodiment, the substrate isselected from the group consisting of a banknote, a brand authenticationtag, a tax stamp, an ID document, an alcoholic bottle, and a tobaccoproduct. Optionally, the first region and/or the second region of thesubstrate may comprise foil, film, UV-coated lacquer, paper, polymer,coated paper, or printed paper. In terms of composition, the substrateoptionally comprises one or more of the following: a fluorinatedpolymer, polyimide, epoxy resin (including glass-filled epoxy resin),polycarbonate, polyester, polyethylene, polypropylene, bi-orientedpolypropylene, mono-oriented polypropylene, polyvinyl chloride, ABScopolymer, wood, paper, metallic foil, glass, banknotes, linen, labels(e.g., self adhesive labels, etc.), synthetic paper, flexiblefiberboard, non-woven polymeric fabric, cloth and other textiles. Otherparticularly advantageous substrates and substrate surfaces includecellulose-based materials such as wood, paper, cardboard, or rayon, andmetallic foil and glass (e.g., thin glass). In another embodiment, thesubstrate comprises a perforated or non-perforated Teslin™ film orcoating, a strong hydrophobic synthetic film or coating manufactured byPPG Industries, Inc.

The compositions employed to form the substrate regions may vary widely.In one embodiment, the composition of the substrate forms a substrateregion. In another embodiment, a separate coating or material forms asubstrate region. Non-limiting examples of compositions that mayemployed to form the regions and surfaces of the present invention, inaddition to those provided above, include foil, film, UV-coated lacquer,paper, coated paper, polymer, and printed paper. In one embodiment, thereflective feature of the present invention comprises a substratecomprising a first region comprising a composition selected from thegroup consisting of foil, film, UV-coated lacquer, paper, coated paper,polymer, and printed paper. The second region similarly may comprise acomposition selected from the group consisting of foil, film, UV-coatedlacquer, paper, coated paper, polymer, and printed paper (so long as itis a different composition than the first region).

In one embodiment, the reflective feature of the present inventioncomprises a substrate having a first region comprising a firstundercoat. The first undercoat optionally comprises a compositionselected from the group consisting of varnishes, offset varnishes, dryoffset varnishes, shellacs, latexes, and polymers. As used herein, theterm “undercoat” refers to a coating disposed underneath a reflectiveelement and on top of a supporting substrate. If the first regioncomprises a first undercoat, the first reflective element, which isdisposed on the first undercoat of the first region, exhibits enhancedreflectivity relative to the reflectivity of the first reflectiveelement in the absence of the first undercoat. The presence of theundercoat may also facilitate adhesion and durability of the firstreflective element.

In a similar embodiment, optionally in addition to employing a firstundercoat, the second region optionally comprises a second undercoat. Asexplained above, the first and second regions of this embodiment of thepresent invention have different surface characteristics, and in thisembodiment the formulation of the first undercoat creates thecharacteristics of the first region, and the formulation of the secondundercoat creates the characteristics of the second region. Preferably,with the second region comprising the second undercoat, the secondreflective element exhibits enhanced reflectivity relative to thereflectivity of the second reflective element in the absence of thesecond undercoat.

In one embodiment, the reflective feature of the present inventionfurther comprises an overcoat, e.g., a first overcoat, disposed on thefirst reflective element. The overcoat optionally comprises acomposition selected from the group consisting of varnishes, offsetvarnishes, dry offset varnishes, shellacs, latexes, and polymers.Preferably, with the first overcoat disposed on the first reflectiveelement, the first reflective element exhibits enhanced reflectivityrelative to the reflectivity of the first reflective element in theabsence of the first overcoat. In addition, with the first overcoatdisposed on the first reflective element, the first reflective elementpreferably exhibits enhanced durability relative to the durability ofthe first reflective element in the absence of the first overcoat. Inthis embodiment, for example, the overcoated first reflective elementpreferably adheres sufficiently to the first region to rate a score of 2or greater, 3 or greater, 4 or greater, or 5 on the ASTM rub testD-5264D92. The overcoated first reflective element on the first regionalso preferably passes the Scotch tape test, discussed above.

Optionally, the first overcoat also is disposed on the second reflectiveelement. Preferably, with the first overcoat disposed on the secondreflective element, the second reflective element exhibits enhancedreflectivity relative to the reflectivity of the second reflectiveelement in the absence of the first overcoat. In addition, with thefirst overcoat disposed on the second reflective element, the secondreflective element preferably exhibits enhanced durability relative tothe durability of the second reflective element in the absence of thefirst overcoat. In this embodiment, for example, the overcoated secondreflective element preferably adheres sufficiently to the second regionto provide a score of 2 or greater, 3 or greater, 4 or greater, or 5 onthe ASTM rub test D-5264D92. The overcoated second reflective element onthe second region also preferably passes the Scotch tape test, discussedabove.

Optionally, the reflective feature further comprises a second overcoatdisposed on the second reflective element. Preferably, with the secondovercoat disposed on the second reflective element, the secondreflective element exhibits enhanced reflectivity relative to thereflectivity of the second reflective element in the absence of thesecond overcoat. In addition, with the second overcoat disposed on thesecond reflective element, the second reflective element preferablyexhibits enhanced durability relative to the durability of the secondreflective element in the absence of the second overcoat. Optionally,the reflective feature comprises a second overcoat disposed on thesecond reflective element, but the reflective feature does not include afirst overcoat (i.e., a separate overcoat covering any portion of thefirst reflective element).

FIG. 1 illustrates a substrate 1 comprising a first region 2 and asecond region 3. The first region 2 has a first surface 4 and aninterface surface 6, which acts to support the second region 3. Thesecond region 3 that is supported on interface surface 6 has a secondsurface 5. The compositions of the first region 2 and the second region3 may vary widely. As a non-limiting example, the first region 2 couldcomprise linen (e.g., in a bank note) and the second region 3 couldcomprise a metallic foil disposed on top of and adhered to the linen.Importantly, the first surface 4 and the second surface 5 have differentsurface characteristics, meaning they have different properties thataffect the level of adherence of a substance (e.g., an ink) to theirrespective surfaces.

In the linen/foil example provided above, the different surfacecharacteristics may comprise different porosities. The linen may, forexample, be substantially more porous than the foil. Also, the differentsurface characteristics may comprise different degrees ofhydrophillicity; for example, the linen may be more hydrophilic than thefoil (which may be hydrophobic). These different surface characteristicsmay render the two surfaces intolerant to receiving a single type of inkbecause a single ink may not possess properties that are compatible withboth surfaces. That is, depending on the degree of the differencebetween the two surface characteristics, a single ink may not possessattributes that render it suitable for printing on both first surface 4and second surface 5. A single ink may, however, be suitable for onesurface, but not the other.

FIG. 1 also illustrates a single non-continuous reflective featurecomprising the numbers “01234” disposed on substrate 1. The reflectivefeature comprises a first reflective element 7 and a second reflectiveelement 8. Specifically, the first reflective element 7 comprises thenumbers “01”, and the second reflective element 8 comprises the numbers“234”. Semantically, the number “1” (disregarding the number “0”) alsocould be considered a first reflective element since it is disposed onthe first region 2, and the number “2” (disregarding the numbers “34”)could be considered a second reflective element since it is disposed onthe second region 3. According to this embodiment of the presentinvention, the first reflective element 7 (however characterized) ismore adherent to the first region 2, e.g., the first surface 4 of thefirst region 2, than the second reflective element 8 would be if it wereformed on first surface 4 of first region 2. Similarly, the secondreflective element 8 ideally is more adherent to the second region 3,e.g., the second surface 5 of the second region 3, than the firstreflective element 7 would be if it were formed on second surface 5 ofsecond region 3.

Although it is contemplated that the optical properties (e.g., color,hue and reflectivity) of the first reflective element 7 may differ fromthe optical properties of the second reflective element 8, preferablythe optical properties of the first reflective element 7 aresubstantially the same as the optical properties of the secondreflective element 8 such that together the two reflective elements forma single reflective feature (e.g., the number “01234” in FIG. 1) thathas a uniform overall appearance to an observer. That is, preferably thetwo reflective elements appear to have similar or substantially the sameoptical properties such that the two reflective elements appear to a layobserver to have been formed from a single ink. Desirably, the formationof a single reflective feature having an overall uniform appearance on asubstrate having multiple regions with different surface characteristicsis very difficult to reproduce for would-be counterfeiters.

The reflective feature shown in FIG. 1 may be formed, for example, bydepositing, e.g., printing, a first ink on first surface 4 andoptionally treating, e.g., curing, the deposited first ink underconditions effective to form the first reflective element 7, and bydepositing, e.g., printing, a second ink on second surface 5 andoptionally treating, e.g., curing, the deposited second ink underconditions effective to form the second reflective element 8.Optionally, the first and second inks are deposited and then treated,e.g., cured, in a single step. The first ink preferably is more adherentto the first region 2, e.g., the first surface 4 of the first region 2,than the second ink would be if it were deposited on first surface 4 offirst region 2. Similarly, The second ink preferably is more adherent tothe second region 3, e.g., the second surface 5 of the second region 3,than the first ink would be if it were deposited on second surface 5 ofsecond region 3. In various embodiments, the first ink may depositedbefore, after, simultaneously with or substantially simultaneously withdeposition of the second ink.

FIG. 2 illustrates another embodiment of the present invention similarto the one described above with reference to FIG. 1, but in which thesubstrate 1 comprises a first region 9 (having first surface 12)situated adjacent second region 10 (having second surface 13), ratherthan having one of the regions disposed on top of another region, e.g.,a foil disposed on top of an underlying linen supporting substrate. Asin FIG. 1, the first surface 12 and the second surface 13 preferablyhave different surface characteristics. The two regions are connected,e.g., adhered, to one another at interface 11.

FIG. 3 illustrates another embodiment of the present invention in whichthe reflective feature comprises a first reflective element 14, whichforms the left portion of the letter “A”, and a second reflectiveelement 15, which forms the right portion of the letter “A”. Thisreflective feature comprises a continuous graphical feature spanningboth the first region and the second region of a substrate. That is,together, the first and second reflective elements 14, 15 form a singlecontinuous reflective feature that extends across interface 11 unlikethe reflective feature “01234” shown in FIGS. 1 and 2, which compriseselements (“01” and “234”) that are non-continuous (e.g., separate) withrespect to one another.

FIG. 4 shows an intermediate feature that may be formed during thefabrication of the reflective feature shown in FIG. 3. As with theembodiment shown in FIGS. 1 and 2, the first reflective element 14 andthe second reflective element 15 shown in FIG. 3 preferably are formedfrom a first ink and a second ink, respectively, the inks being suitedfor deposition, e.g., printing, onto the first substrate surface 12 andthe second substrate surface 13, respectively. As discussed above, thefirst ink may be deposited before, after, simultaneously with orsubstantially simultaneously with deposition of the second ink. Theintermediate feature shown in FIG. 4 would be formed after deposition ofthe first ink to form the first reflective element 14, but prior todeposition of a second ink to form the second reflective element 15 (theright portion of the letter “A”) shown in FIG. 3.

Processes for Forming a Reflective features on Regions of a SubstrateHaving Different Surface Characteristics

In another embodiment, the invention is to a process for forming areflective feature, e.g., any of the features shown in FIGS. 1-4, theprocess comprising the steps of: providing a substrate comprising afirst region and a second region, the two regions preferably havingdifferent surface characteristics from one another; direct writeprinting, e.g., ink jet printing (piezo-electric, thermal ink jet,drop-on-demand or continuous ink jet (CIJ) printing), a first ink ontothe first region to form a first reflective element; and direct writeprinting, e.g., ink jet printing (piezo-electric, thermal,drop-on-demand or continuous ink jet printing), a second ink onto thesecond region to form a second reflective element, wherein the first inkis more adherent than the second ink to the first region. Ideally, thesecond ink is more adherent than the first ink to the second region.

Optionally, the substrate further comprises a third region having adifferent surface characteristics than either the first region or thesecond element, and the process further comprises the step of directwrite printing, e.g., ink jet printing (piezo-electric, thermal,drop-on-demand ink jet, or continuous ink jet (CIJ) printing), a thirdink onto the third region to form a third reflective element, andwherein the third ink is more adherent than the first ink or the secondink to the third region. Of course, more than three inks may be used toform, for example, more than three reflective elements, as discussedabove.

The process optionally includes steps of treating, e.g., curing, thedeposited inks (e.g., one or more of the first, second and/or optionalthird ink) so as to facilitate removal of the liquid components of theinks (e.g., vehicles) and convert the deposited inks to a highly robust,durable reflective features. The treating optionally comprises simplyallowing the deposited ink or inks to dry. In this embodiment, thevehicle in the deposited inks is allowed to vaporize (with or withoutapplication of one or more of heat, pressure, IR radiation and/or UVradiation) into the atmosphere to form the feature, e.g., security ordecorative feature. After drying, the nanoparticles yielded from theinks during drying have a relatively high degree of reflectivity,meaning the nanoparticle film or layer formed from the ink or inkspossesses a high degree of optical smoothness (e.g., having a surfaceroughness less than 100 nm). With optional subsequent additionaltreating steps, e.g., heating, rolling, pressing, UV curing, IR curing,etc., the reflectivity increases, meaning that the optical smoothness ofthe nanoparticle film or layer (e.g., the first reflective elementand/or the second reflective element) is increased relative to thereflectivity in the case of just allowing the deposited ink to drywithout an additional treating step. If the inks include metallicnanoparticles, the treating may also allow adjacent nanoparticles tosinter or neck with one another so as to provide increased reflectivityand durability. Surface roughness of the feature (e.g., the first andsecond reflective elements thereof) after curing by one or more ofheating, rolling, pressing, UV curing, or IR curing, may be on the orderof 50 nm or less. Thus, depending on how the deposited inks are treated,the feature optionally comprises first and/or second reflective elementscomprising the nanoparticles, the first and/or second elements having aroute mean square surface roughness that is less than about 100 nm, lessthan about 75 nm or less than about 50 nm. In one embodiment, thedeposited first and second inks may be cured in a single treating step(after deposition of the inks) or in multiple treating steps, e.g., afirst ink may be deposited and then cured, followed by deposition of asecond ink and curing of the second ink.

The utilization of direct write printing to form the reflective featuresof the present invention is highly desirable in that it provides theability to create features that comprise variable information, meaninginformation that is individualized for a product unit, such as, but notlimited to, serialized data. For example, a serial number is onenon-limiting type of variable information. Other types of variableinformation include: counters, lettering, sequential symbols,alphanumeric variable information, non-serialized variable information(variable information that is not sequential), and combinations thereof.Thus, in one embodiment, the reflective feature, e.g., reflectivesecurity feature or reflective decorative feature, comprises, exhibitsor displays variable information.

In addition to being able to individualize a document, tag, etc., theability to incorporate variable information in a feature, e.g.,reflective feature, provides even further anti-counterfeiting measuresnot recognized or available until now. For even further increasedsecurity, the feature optionally comprises variable information such asa serial number comprising a plurality of numbers, where at least one ofthe numbers is disposed or printed on the first surface of the firstregion with a first ink, and at least one of the numbers is disposed orprinted on the second surface of the second region with a second ink. Ineffect, a serial number comprises multiple numbers, each of which may becharacterized as a separate element of the reflective feature, at leasttwo numbers of which are formed from different inks specifically suitedfor different surfaces.

As indicated above, the reflective features preferably are formed frommultiple inks, each ink preferably being formulated to optimally adhereto a given substrate surface (e.g., first or second surface of first orsecond regions, respectively) and form a different reflective element.Unlike the adherence test discussed above for determining the level ofadherence of a solid reflective element onto a substrate region, theability of a fluid ink to adhere to a substrate surface may becharacterized by the contact angle formed between a respective inkdroplet and the surface on which the ink is deposited, e.g., printed. Asused herein, the term “contact angle” means the angle at which aliquid/vapor interface meets the substrate surface (e.g., first surfaceor second surface). The contact angle, θ, of an ink with a surface isdetermined primarily by the interfacial energies of the materialsinvolved, as related by the equation:

γ_(sv)=γ_(s1)+γ_(1v) cos θ

where γ_(sv) is solid-vapor interfacial energy, γ_(s1) is solid-liquidinterfacial energy, and γ_(1v) is liquid-vapor interfacial energy. Forpurposes of the present specification and appended claims, the contactangle is determined by using a Kruss Goniometer and measuring the staticcontact angle for relatively smooth surfaces and dynamic contact anglesfor slightly rough surfaces.

Generally, if the contact angle is less than about 90°, the ink isconsidered “wetting” and desirably can spread on the surface. For theliquid to completely wet the surface, the contact angle should approachzero. For spreading to occur, the surface energy of the solid must begreater than the combination of the surface tension of the liquid andthe interfacial tension between the solid and the liquid. Although thereare exceptions, generally speaking, the more adherent (wetting) an inkis to a particular substrate region, the more adherent the resultingreflective element will be to that substrate region.

FIG. 5 illustrates the contact angle, θ₁, for an ink droplet 16 thatexhibits good wetting characteristics on substrate surface 17. Desirablewetting characteristics are reflected by an ink having a contact anglewith a certain substrate surface that is less than 90°, preferably lessthan about 75°, more preferably less than about 45°, or less than about30°. A contact angle of greater than 90° is generally indicative of anon-wetting ink. FIG. 6 illustrates a non-wetting ink droplet 18 onsubstrate surface 17 with a contact angle, O₂, that is greater than 90°.

In a preferred embodiment, after deposition (e.g., printing), the firstink on first region, e.g., first surface of the first region, preferablyhas a contact angle less than 90° (is wetting), e.g., less than about75°, less than about 45°, less than about 30°, and most preferably fromabout 1° to about 20°. Optionally, the second ink on second region,e.g., second surface of the second region, preferably has a contactangle less than 90° (is wetting), e.g., less than about 75°, less thanabout 45°, less than about 30°, and most preferably from about 10 toabout 20°. Hereinafter, the contact angle of the first ink with thefirst region (e.g., first surface thereof) is referred to as the firstcontact angle, and the contact angle of the second ink with the secondregion (e.g., second surface thereof) is referred to as the secondcontact angle.

As indicated above, the first ink preferably is more adherent than thesecond ink to the first region, e.g., the first surface of the firstregion. By “more adherent” it is meant that the first contact angle isless than (optionally by at least about 5°, at least about 10°, at leastabout 20°, at least about 30°, at least about 45°, at least about 60° orat least about 80°) the contact angle that would be created if thesecond ink were deposited on the first region, e.g., on the firstsurface of the first region. Conversely, it has been indicated that thesecond ink preferably is more adherent than the first ink to the secondregion, e.g., the second surface of the second region. By this it ismeant that the second contact angle is less than (optionally by at leastabout 5°, at least about 10°, at least about 20°, at least about 30°, atleast about 45°, at least about 60° or at least about 80°) the contactangle that would be created if the first ink were deposited on thesecond region, e.g., on the second surface of the second region.

Many properties of inks and substrates will impact the contact anglethat is created therebetween. By way of non-limiting examples, wettingcharacteristics, porosity, surface energy, charge, bonding andhydrophilicity/hydrophobicity are surface characteristics that mayaffect the level of adherence of a substance to a surface. Properties ofinks used to form the reflective features of the invention that mayimpact the level of adherence to a given substrate surface includesurface tension, hydrophilicity/hydrophobicity, charge, viscosity, andvapor pressure.

Inks may be modified to provide the desired physical characteristicsthat render them suitable for deposition on a specific region by avariety of different methods. As one example, the surface tension andhydrophilicity/hydrophobicity of an ink may be modified by adding orreducing the amount of surfactant contained in the ink. In anotherembodiment, the relative amounts and types of vehicles employed in theink may be modified to arrive at an ink having the desired surfacetension, hydrophilicity/hydrophobicity, viscosity and vapor pressure. Inanother embodiment, one or both the first region and the second regionare treated, e.g., by laser-treating, chemical treating, e.g., withozone, to improve the adherence of the first and second inks,respectively, thereto.

The inks used to form reflective elements may comprise a variety ofdifferent compositions. In various embodiments, an ink used to form areflective element may comprise one or more of the following:particulates (preferably metallic nanoparticulates), one or more metalprecursors, one or more vehicles, colorants (e.g., dyes or pigments), anant-agglomeration agent, a reducing agent, one or more additives (suchas, but not limited to surfactants, polymers, biocides, thickeners,binders, etc.) or other components.

In a preferred embodiment, either or both the first ink and/or thesecond ink as well as the reflective features formed therefrom comprisemetallic nanoparticles. Thus, in a preferred embodiment, either or boththe first reflective element and/or the second reflective element, whichare formed from the first and second inks, respectively, also comprisemetallic nanoparticles. Preferably, the metallic nanoparticles in eitheror both the first reflective element and/or the second reflectiveelement form a highly reflective film or films. By “highly reflective,”it is meant that the nanoparticles when formed in a film exhibit atleast some degree of non-diffuse or non-Lambertian reflectivity. Thatis, the nanoparticle film or films (as well as the overall features ofthe invention) preferably exhibit some degree of specular reflectivity,optionally some degree of colored specular reflectivity. It iscontemplated, however, that the nanoparticle film(s), the first and/orsecond reflective elements and/or the reflective features themselves mayexhibit some degree of diffuse reflectivity, in addition to specularreflectivity. Reflective elements comprising metallic nanoparticles havebeen found to exhibit enhanced reflectivity, particularly enhancedspecular reflectivity, over conventional features.

As used herein, the term “metallic nanoparticles” means particlescomprising a metal or metallic characteristic and having an averageparticle size of less than about 1 μm. One skilled in the art wouldappreciate that there are many techniques for determining the averageparticle size of a population of particles, scanning electron microscopy(SEM) being a particularly preferred technique. The average particlesize of particles smaller than about 1 μm is also determinable usingquasi-elastic light scattering (QELS) techniques (e.g., using a Malvern™ZetaSizer™). By “comprising a metal” it is meant all or a portion of theparticles optionally included in the reflective features of the presentinvention include, in whole or in part, a metal (e.g., an elementalmetal (zero oxidation state) or a mixture or alloy of metals) or ametal-containing compound (e.g., a metal oxide or metal nitride). Thus,in a preferred embodiment, the optional metallic nanoparticles comprisea component selected from the group consisting of a metal, a metalalloy, and a metal-containing compound (e.g., a metal oxide).Additionally or alternatively, the metallic nanoparticles may comprise acomponent having a metallic characteristic. The term “metalliccharacteristic” means a reflective or lustrous optical property similarto a metal. For example, a component may exhibit a metalliccharacteristic by virtue of it having a small electronic band gap.

As indicated above, the optional metallic nanoparticles preferably havean average particle size of less than about 1 μm. In another embodiment,the metallic nanoparticles have an average particle size of less thanabout 500 nm, more preferably less than about 250 nm, even morepreferably less than about 100 nm, and most preferably less than about80 nm. The metallic nanoparticles optionally have an average particlesize greater than about 5 nm, greater than about 10 nm, greater thanabout 20 nm, greater than about 25 nm, greater than about 30 nm, greaterthan about 40 nm, greater than about 50 nm, greater than about 100 nm,greater than about 250 nm or greater than about 500 nm. In terms ofranges, the metallic nanoparticles optionally have an average particlesize in the range of from about 20 nm to about 1 μm, from about 25 nm toabout 1 μm, from about 30 nm to about 1 μm, from about 40 nm to about 1μm, from about 50 nm to about 500 nm, from about 20 nm to about 100 nm,from about 50 nm to about 100 nm, or from about 50 nm to about 80 nm.The metallic nanoparticles may have a unimodal or multi-modal (e.g.,bimodal, trimodal, etc.) particle size distribution.

Non-limiting examples of metals for use in the optional metallicnanoparticles and features of the present invention include transitionmetals as well as main group metals such as, for example, silver, gold,copper, nickel, cobalt, palladium, platinum, indium, tin, zinc,titanium, chromium, tantalum, tungsten, iron, rhodium, iridium,ruthenium, osmium, lead and mixtures thereof. The metallic nanoparticlesoptionally comprise an alloy comprising at least two metals beingselected from the group consisting of: silver, gold, copper, nickel,cobalt, palladium, platinum, indium, tin, zinc, titanium, chromium,tantalum, tungsten, iron, rhodium, iridium, ruthenium, osmium, and lead.Non-limiting examples of preferred metals for use in the presentinvention include silver, gold, zinc, tin, copper, nickel, cobalt,rhodium, palladium and platinum—silver, copper and nickel beingparticularly preferred. The metallic nanoparticles optionally comprise ametal selected from the group consisting of silver, gold, zinc, tin,copper, platinum and palladium (including combinations thereof).Non-limiting examples of metal-containing compounds or components thatexhibit metallic characteristics and that may be useful as metallicnanoparticles of the features and inks of the present invention includemetal oxides, metal nitrides, metal carbides (e.g., titanium nitride ortantalum nitride), metal sulphides and some semiconductors. Themetal-containing compound(s) preferably have a small electronic band gapthat gives rise to metallic properties or characteristics. Anon-limiting list of exemplary metal oxides includes bronzes such astungsten bronzes including hydrogen tungsten oxide, sodium tungstenoxide and lithium tungsten oxide as well as other bronzes such asphosphor bronzes. Additional tungsten oxides are described in PublishedU.S. Patent Application No. 2005/0271566A1, which published Dec. 8,2005, the entirety of which is incorporated herein by reference. In oneaspect, the metallic nanoparticles comprise a mineral having a metalliccharacteristic. A non-limiting list of exemplary minerals suitable forthe metallic nanoparticles includes marcasites and pyrites. In anotherembodiment, the metallic particles and/or the metallic nanoparticlescomprise an enamel or a glass/metal composite that provides a metalliccharacteristic. In one embodiment, the metallic nanoparticles comprise apearlescent material and/or an opalescent material that provides ametallic characteristic.

The features of the present invention (as well as the inks used to make,form, print, or create the features of the present invention) also, inone embodiment, comprise mixtures of two or more different metallicnanoparticles. In another embodiment, the features of the presentinvention comprise metallic nanoparticles that comprise two or moremetals in the form of an alloy or a mixture of metals or metalcontaining compounds. Non-limiting examples of alloys useful as metallicnanoparticles of the invention include Cu/Zn, Cu/Sn, Ag/Ni, Ag/Cu,Pt/Cu, Ru/Pt, Ir/Pt and Ag/Co. Optionally, the metallic particles and/ornanoparticles comprise an alloy such as bronze, tungsten bronzes orbrass. Also, in an embodiment, the metallic nanoparticles have acore-shell structure made of two different metals such as, for example,a core comprising nickel and a shell comprising silver (e.g. a nickelcore having a diameter of about 20 nm surrounded by an about 15 nm thicksilver shell). In another embodiment, the core-shell structure may becomprised of a metal oxide core with another metal oxide coating. Anon-limiting example is a nanoparticle core-shell structure comprising amica core and a titania coating. In another embodiment, the metallicnanoparticles comprise metal-effect particles and/or pigments. Onemethod for creating metal effect pigments is to deposit thin layers ofone metal oxide or ceramic on the surface of another (e.g. TiO₂ onmica). Metal-effect pigments are further described in CENEAR Vol. 81,No. 44, pp. 25-27 (Nov. 3, 2003) (ISSN 0009-2347), the entirety of whichis incorporated herein by reference.

Metallic nanoparticles suitable for use in the inks to form theinventive reflective features can be produced by a number of methods.For example, the metallic nanoparticles may be formed by spraypyrolysis, as described, for example, in U.S. Provisional PatentApplication No. 60/645,985, filed Jan. 21, 2005, or in an organicmatrix, as described in U.S. patent application Ser. No. 11/117,701,filed Apr. 29, 2005, the entireties of which are fully incorporatedherein by reference. A non-limiting example of one preferred method ofmaking metallic particles and metallic nanoparticles, is known as thepolyol process, and is disclosed in U.S. Pat. No. 4,539,041, which isfully incorporated herein by reference. A modification of the polyolprocess is described in, e.g., P.-Y. Silvert et al., “Preparation ofcolloidal silver dispersions by the polyol process” Part 1—Synthesis andcharacterization, J. Mater. Chem., 1996, 6(4), 573-577; Part 2—Mechanismof particle formation, J. Mater. Chem., 1997, 7(2), 293-299, bothdisclosures of these documents are fully incorporated by referenceherein. Briefly, in the polyol process a metal compound is dissolved in,and reduced or partially reduced by a polyol such as, e.g., a glycol, atelevated temperature to afford corresponding metal particles. In themodified polyol process, the reduction is carried out in the presence ofa dissolved anti-agglomeration substance, preferably a polymer, mostpreferably polyvinylpyrrolidone (PVP).

A particularly preferred modification of the polyol process forproducing metallic particles, especially metallic nanoparticles, isdescribed in co-pending U.S. patent application Ser. Nos. 60/643,577filed Jan. 14, 2005, 60/643,629 filed Jan. 14, 2005, and 60/643,578filed Jan. 14, 2005, and co-pending U.S. patent application Ser. Nos.11/331,211 filed Jan. 13, 2006, 11/331,238 filed Jan. 13, 2006, and11/331,230 filed Jan. 13, 2006, which are all herein fully incorporatedby reference. In a preferred aspect of a modified polyol process, adissolved metal compound (e.g., a silver compound such as silvernitrate) is combined with and reduced by a polyol (e.g., ethyleneglycol, propylene glycol and the like) at an elevated temperature (e.g.,at about 120° C.) and in the presence of a polymer, preferably aheteroatom-containing polymer such as PVP.

Each of the first and second inks preferably comprises a vehicle forimparting desired flow characteristics to the ink. Typically, thevehicles will be carefully selected to provide first and second inkformulations that possess desirable properties for interacting with thefirst and second regions, respectively, on which they are deposited.Since the surface characteristics of the first and second regions differfrom one another, the vehicles selected for the first and second inkstypically will differ from one another, whether by type or relativeamounts, so as to impart the desired properties for interacting with thefirst and second regions, respectively.

The vehicles for use in the ink, e.g., direct write, thermal,piezo-electric or continuous ink jet ink or digital ink, is preferably aliquid that is capable of stably dispersing the metallic nanoparticles,if present. For example, vehicles are preferred that are capable ofaffording an ink dispersion that can be kept at room temperature forseveral days or even one, two, three weeks or months or even longerwithout substantial agglomeration and/or settling of the metallicnanoparticles. To this end, it is also preferred for the vehicle to becompatible with the surface of the metallic nanoparticles. It isparticularly preferred for the vehicle to be capable of dissolving theanti-agglomeration substance, if present, to at least some extent,without removing it from the metallic nanoparticles. In one embodiment,the vehicle comprises (or predominantly consists of) one or more polarcomponents (solvents) such as, e.g., a protic solvent, or one or moreaprotic, non-polar components, or a mixture thereof. The vehicle, in anembodiment, is a solvent selected from the group consisting of alcohols,polyols, amines, amides, esters, acids, ketones, ethers, water,saturated hydrocarbons, unsaturated hydrocarbons, and mixtures thereof.

Where the features of the invention are printed, formed or createdthrough direct-write printing, such as ink-jet printing e.g., thermal,piezo-electric or continuous ink jet printing, or digital printing, thevehicle is preferably selected to effectively work with direct-writeprinting tool(s), such as, e.g., an ink-jet head, a digital head, andcartridges, particularly in terms of viscosity and surface tension ofthe ink composition.

In a preferred aspect, for piezo-electric ink jet inks, the vehiclecomprises a mixture of at least two solvents, optionally at least twoorganic solvents, e.g., a mixture of at least three organic solvents, orat least four organic solvents. The use of more than one solvent ispreferred because it allows, inter alia, to adjust various properties ofa composition simultaneously (e.g., viscosity, surface tension, contactangle with intended substrate etc.) and to bring all of these propertiesas close to the optimum values as possible. In one embodiment, thevehicle comprises a mixture of ethylene glycol, ethanol and glycerol.Non-limiting examples of vehicles are disclosed in, e.g., U.S. Pat. Nos.5,853,470; 5,679,724; 5,725,647; 4,877,451; 5,837,045 and 5,837,041, theentire disclosures of which are incorporated by reference herein.

For thermal ink jet inks, the vehicle preferably comprises a mixture ofat least two solvents, optionally at least two organic solvents, e.g., amixture of at least three organic solvents, or at least four organicsolvents. The use of more than one solvent is preferred because itallows, inter alia, to adjust various properties of a compositionsimultaneously (e.g., viscosity, surface tension, contact angle withintended substrate etc.) and to bring all of these properties as closeto the optimum values as possible—particularly so that the first andsecond inks, respectively, are well-suited for deposition onto the firstand second regions, respectively. Preferably, for thermal ink jetprinting applications, the vehicle comprises water, optionally with oneor more other vehicles. In one embodiment, the vehicle comprises amixture of propylene glycol and water.

In a preferred embodiment, particularly for thermal ink jet printingapplications, the vehicle comprises water. For example, the vehicleoptionally comprises at least 30 wt. % water, at least 40 wt. % water,at least 50 wt. % water, at least 60 wt. % water, or at least 70 wt. %water, based on the total weight of the vehicle.

It is desirable to also take into account the requirements, if any,imposed by the deposition tool (e.g., in terms of viscosity and surfacetension of the ink) and the surface characteristics (e.g., acidity,hydrophilicity or hydrophobicity) of the intended substrate in selectingthe vehicle of choice. Although the desired ink viscosity may dependgreatly on the specific deposition tool implemented, inks used to formthe features of the present invention, particularly those intended forink-jet printing with a piezo head, preferably have a viscosity(measured at 20° C.) that is not lower than about 2 centipoise (cP),e.g., not lower than about 12 cP, or not lower than about 15 cP, andoptionally not higher than about 50 cP, e.g., not higher than about 40cP, not higher than about 30 cP, or not higher than about 25 cP. In oneembodiment, the ink has a viscosity (measured at 20° C.) that is greaterthan about 0.5 cP, e.g., greater than about 1.0 cP, or greater thanabout 1.3 cP, and less than about 10 cP, e.g., less than about 7.5 cP,less than about 5 cP, or less than about 4 cP.

The vehicle preferably provides the inks with a surface tension(measured at 20° C.) ranging from about 10 to about 60 dynes/cm, e.g.,from about 10 to about 50 dynes/cm or from about 10 to about 40dynes/cm.

The inks, e.g., thermal or piezo-electric ink jet inks or digital inks,in an embodiment can further comprise one or more additives, such as,but not limited to, adhesion promoters, rheology modifiers, surfactants,wetting angle modifiers, humectants, crystallization inhibitors,binders, and the like. The inks optionally further comprise a protectivecoating material such as a lacquer, polymer or a varnish. Such additivesare fully described in co-pending U.S. patent application Ser. No.11/331,233, previously incorporated herein by reference. Other inkformulations are provided in co-pending U.S. patent application Ser. No.11/331,185, filed Jan. 13, 2006, the entirety of which is incorporatedherein by reference.

A preferred additive for inclusion in either or both the first inkand/or the second ink includes surfactants. The amount and type ofsurfactant may be carefully controlled so as to provide first and/orsecond inks that are well-suited for deposition on the first and secondregions, respectively, of the substrate. The types of surfactant(s) thatmay be included in the first and/or second ink may vary widely. Somenon-limiting examples of preferred surfactants for use in thisembodiment of the present invention include fluoronated surfactants,such as FLUORAD® (3M), ZONYL® (duPont); non-ionic surfactants such asTERGITOL®, SURFYNOL®, or siloxanes; and ionic surfactants. Othersurfactants suitable for inclusion in the first and/or second inks arelisted in U.S. Provisional Patent Application Ser. Nos. 60/643,577 filedJan. 14, 2005, 60/643,629 filed Jan. 14, 2005, and 60/643,578 filed Jan.14, 2005, the entireties of which are incorporated herein by reference,and in co-pending Non-Provisional U.S. patent application Ser. Nos.11/331,211 filed Jan. 13, 2006, 11/331,238 filed Jan. 13, 2006, and11/331,230 filed Jan. 13, 2006, the entireties of which are incorporatedherein by reference.

Multi-Layered Reflective features

In another aspect, the present invention is directed toward a reflectivefeature comprising a substrate having a first surface; a first coatingdisposed on the first surface and having a second surface; and areflective element having a third surface and comprising nanoparticles,preferably metallic nanoparticles, disposed, at least in part, on thesecond surface. The first surface may exhibit a wide range of surfacecharacteristics in terms of porosity, hydrophilicity/hydrophobicity,acidity, etc. The primary purpose of the first coating is to planarizeand/or reduce the porosity of the underlying substrate. It has beendiscovered that by planarizing and/or reducing the porosity of thesubstrate with the first coating, the reflectivity of the subsequentlyformed reflective element (preferably comprising metallic nanoparticles)is greater than it would be in the absence of the first coating. Thatis, the reflective feature preferably exhibits enhanced reflectivityrelative to the reflectivity of the reflective feature in the absence ofthe first coating.

In one embodiment, the substrate comprises a first surface comprisingtwo regions having different surface characteristics, and the firstcoating covers at least a portion of both regions so as to provide auniform (second) surface covering at least a portion of both regions.Subsequently, a single ink may then be applied, e.g., printed, onto theuniform (second) surface and over the two regions so as to form areflective element that spans both regions notwithstanding the differentsurface characteristics of the two regions. In this embodiment, ratherthan providing separate first and second inks for forming first andsecond reflective elements, respectively, as described above withreference to FIGS. 1-4, the coating is formed of a single material thatis capable of adhering to both regions, and a single ink is thenapplied, e.g., printed, directly on the first coating and over bothregions.

The first coating preferably has a porosity less than the porosity ofthe substrate and the first surface of the substrate. In one embodiment,the first coating comprises a material selected from the groupconsisting of varnishes, offset varnishes, dry offset varnishes,shellacs, latexes and polymers. The invention, however, is not limitedto first coatings comprising these materials, as the first coating maycomprise any material that lowers the porosity or which can planarizethe first surface of the substrate. As the reflective element may be atleast partially semitransparent, a portion of the first coating may beviewable through the reflective element. Optionally, the first coatingcomprises a colorant. By way of non-limiting examples, the colorant maybe a dye or pigment. Utilizing a colorant affects the appearance of thereflective feature by changing the apparent color thereof. The color ofthe substrate when viewed through a first coating comprising a colorantmay differ from the color of the substrate viewed through the firstcoating in the absence of a colorant. Additionally, the presence of thecolorant in the first coating may modify the apparent color of thenanoparticles contained in the reflective element that is disposed ontop of the first coating. For example, if a yellow colorant is containedin the first coating, and the reflective element comprises silvernanoparticles, the overall reflective feature may exhibit a goldmetallic luster, rather than the silver native color of silvernanoparticles.

In one embodiment, the nanoparticles in the reflective element comprisemetallic nanoparticles, as fully described above. By way of non-limitingexamples, the metallic nanoparticles may comprise a metal selected fromthe group consisting of silver, gold, zinc, tin, copper, platinum, andpalladium, and alloys thereof. Optionally, a majority of the metallicnanoparticles are necked with at least one adjacent metallicnanoparticle. Optionally, the average distance between adjacent metallicparticles is less than about 700 nm, e.g., less than about 400 nm, lessthan about 200 nm, less than about 100 nm, less than about 30 nm, lessthan about 10 nm, or less than about 1 nm. Optionally, the metallicnanoparticles have an average particle size of less than about 200 nm,e.g., less than about 150 nm, less than about 100 nm, less than about 75nm or less than about 50 nm. Preferably, the metallic nanoparticles havean average particle size of from about 5 nm to about 100 nm. In anotherembodiment, the nanoparticles comprise phosphorescent nanoparticles.

In one embodiment, the reflective feature further comprises a secondcoating having a fourth surface disposed at least in part on the thirdsurface. By way of non-limiting examples, the second coating maycomprise material selected from the group consisting of varnishes,offset varnishes, dry offset varnishes, shellacs, latexes and polymers.Preferably, the second coating is transparent. As used herein, the term“transparent” means capable of allowing light to pass therethrough,e.g., through a translucent layer. The primary purpose of the secondcoating is to protect the underlying layers from, for example, moisture,and everyday wear-and-tear. Additionally, the second coating may enhancethe reflectivity of the reflective feature if, for example, the fourthsurface possesses specular reflectance. Optionally, the second coatingfurther comprises a colorant, e.g., a dye, pigment or phosphor, whichmodifies the color or photoluminescence of the feature.

FIG. 7 illustrates an exploded view of a multi-layered structure of afeature according to this embodiment of the invention, and FIG. 8illustrates a non-exploded view of the same feature. FIGS. 7 and 8illustrate a substrate 19 having first surface 20. First surface 20 maybe substantially porous or comprise a rough surface on a microscopiclevel, the surface comprising multiple peaks and valleys, as shown ininset 27. A first coating, which comprises a second surface 22, isdisposed on the first surface 20. As shown in inset 27, the secondsurface 22 preferably is less porous than the first surface 20 and/oracts to planarize substrate 19. A reflective element 23, which has athird surface 24, preferably comprising nanoparticles, e.g., metallicnanoparticles, preferably reflective metallic nanoparticles, is disposedon second surface 22. The reduced porosity and/or more planar nature ofthe second surface relative to the first surface 20 causes thenanoparticles in the reflective element 23, to be retained on the secondsurface, thereby concentrating the nanoparticles in a single plane andenhancing reflectivity. FIGS. 7 and 8 also illustrate optional secondcoating 25, which comprises fourth surface 26, disposed on secondsurface 22 of first coating 21 as well as on top of third surface 24 ofreflective element 23. The second coating 25 acts to protect thereflective element 23 as well as provide enhanced reflectivity to theoverall reflective feature.

Preferably, the reflective element is highly reflective. In oneembodiment, the reflective element comprises a reflective layer. Thereflective layer optionally is at least partially semitransparent. Asused herein, the term “semitransparent” means capable of allowing atleast some light to pass therethrough, e.g., through openings and/orthrough a translucent layer, while optionally absorbing a portion of thelight. The reflective layer may also be continuous or non-continuous.

In another embodiment, the reflective element comprises a plurality ofreflective images, e.g., a plurality of reflective microimages having anaverage largest dimension of less than about 0.5 mm, e.g., less thanabout 0.4 mm, less than about 0.3 mm, less than about 0.2 mm, or lessthan about 0.1 mm. Optionally, at least one microimage comprisesvariable data.

In one embodiment, an image is disposed on at least one of the firstsurface or the second surface, and at least a portion of the image isviewable through the reflective element when viewed at a first anglerelative to the third surface, and at least a portion of the image is atleast partially obscured when viewed from a second angle relative to thethird surface. In this embodiment, therefore, the reflective element atleast partially obscures the image, depending on the viewing angle.Optionally, the second angle is about 180° minus the angle of incidentlight, relative to the third surface. By way of non-limiting examples,the image may be formed by direct write printing, intaglio printing,gravure printing, lithographic printing, and flexographic printing, and,by way of non-limiting examples, the image may be a black and whiteimage, a color image, a hologram, a watermark, and a UV fluorescentimage. Optionally, the image is in the form of text or a serial number.

In other embodiments, the invention includes the first coating and thereflective element but not the second coating. In another embodiment,the invention includes the reflective element and the second coatingdisposed thereon, but not the first coating.

In one aspect, the invention relates to processes for forming theabove-described multi-layered reflective features, one processcomprising the steps of: providing a substrate having a first surface;forming, e.g., printing, optionally through a direct write printingprocess, e.g., a piezo-electric, thermal, drop-on-demand or continuousink jet printing process, a first coating on the first surface, thefirst coating having a second surface; and forming, e.g., printing,optionally through a direct write printing process, e.g., apiezo-electric, thermal, drop-on-demand or continuous ink jet printingprocess, a reflective element on the second surface, the reflectiveelement having a third surface comprising nanoparticles, preferablymetallic nanoparticles. In one embodiment, the reflective element formedcomprises a reflective layer that is at least partially semitransparent.The reflective layer may be continuous or non-continuous. Preferably,the first coating formed renders the reflective feature formed morereflective than it would be in the absence of the first coating.

Optionally, the nanoparticles employed in the process of the inventioncomprise metallic nanoparticles. Optionally, a majority of the metallicnanoparticles in the formed reflective element are necked with at leastone adjacent metallic nanoparticle. By way of non-limiting examples, themetallic nanoparticles may comprise a metal selected from the groupconsisting of silver, gold, zinc, tin, copper, platinum, and palladium,and alloys thereof.

In one embodiment, the step of the forming the first coating comprisesdepositing a first ink onto the first surface and treating the depositedfirst ink under conditions effective to form the first coating. Thefirst ink may comprise, for example, a material selected from the groupconsisting of a varnish, an offset varnish, a dry offset varnish, ashellac, latex, and a polymer. In other embodiments, the first inkcomprises a lacquer, an enamel, a glass, a glass/metal composite, orpolymer, which may be applied (optionally printed). Other non-limitingexemplary substances useful for inclusion in the first ink includelacquers, fluorosilicates, fluorinated polymers (e.g., Zonyl products),shellac (or other similar clear coat technologies), acrylates, UVcurable acrylates, polyurethanes, etc., or a combination thereof. Thefirst ink optionally is deposited on the first surface by a printingprocess selected from the group consisting of direct write printing(e.g., ink jet (e.g., piezo-electric, thermal, drop-on-demand orcontinuous ink jet printing) or digital printing), intaglio printing,gravure printing, offset printing, lithographic printing andflexographic printing processes. Preferably, the depositing comprisesdirect write printing (e.g., ink jet (e.g., piezo-electric, thermal,drop-on-demand or continuous ink jet printing) or digital printing) thefirst ink onto the first surface. In one embodiment, one or more dyes orpigments are included to the first ink and provide color to the firstcoating and ultimately formed feature. See Ernest W. Flick, Printing Inkand Overprint Varnish Formulations, Recent Developments (NoyesPublications 1991) (ISBN 0-8155-1259-7), and Ernest W. Flick, PrintingInk and Overprint Varnish Formulations, Second Edition (NoyesPublications 1999) (ISBN 0-8155-1440-9), the entireties of which areincorporated herein by reference, or an overview of various coatingformulations that may be employed for the first ink. The treating of thedeposited first ink preferably comprises drying, optionally with heatingand/or application of UV radiation to the deposited first ink. Somespecific preferred first ink compositions for forming the first coatinginclude RJE A8070 lacquer medium cvec12414 from Cavalier Inks andCoatings (Richmond, Va.); CK-49HG-1 and CK-1250 from Cork IndustriesInc. (Folcroft, Pa.); and NiCoat (noncurl 8020) from Gans Ink and SupplyCo. (Los Angeles, Calif.).

In another embodiment, the step of forming the reflective elementcomprises depositing a second ink onto the second surface and treatingthe deposited second ink under conditions effective to form thereflective element. The composition and properties of the second ink maybe as described above with reference to the inks used to form thereflective elements of the other reflective features of the presentinvention. Optionally, the depositing comprises direct write printing,e.g., a piezo-electric, thermal, drop-on-demand or continuous ink jetprinting, the second ink onto the second surface. Optionally, thetreating comprises allowing the second ink to dry, heating the depositedsecond ink and/or applying UV radiation to the deposited second ink. Inanother embodiment, the treating comprises applying UV radiation to thedeposited second ink.

In one embodiment, the process further comprises the step of forming asecond coating on the third surface, the second coating having a fourthsurface. Optionally, the second coating is transparent. In oneembodiment, the step of the forming the second coating comprisesdepositing a third ink onto the second surface and treating thedeposited third ink under conditions effective to form the secondcoating. The third ink may comprise, for example, a material selectedfrom the group consisting of a varnish, an offset varnish, a dry offsetvarnish, a shellac, latex, and a polymer. In other embodiments, thethird ink comprises a lacquer, an enamel, a glass, a glass/metalcomposite, or polymer, which may be applied (optionally printed). Othernon-limiting exemplary substances useful for inclusion in the third inkinclude lacquers, fluorosilicates, fluorinated polymers (e.g., Zonylproducts), shellac (or other similar clear coat technologies),acrylates, UV curable acrylates, polyurethanes, etc., or a combinationthereof. The third ink optionally is deposited on the second surface bya printing process selected from the group consisting of direct writeprinting (e.g., ink jet (e.g., piezo-electric, thermal, drop-on-demandor continuous ink jet printing) or digital printing), intaglio printing,gravure printing, offset printing, lithographic printing andflexographic printing processes. Preferably, the depositing comprisesdirect write printing (e.g., ink jet (e.g., piezo-electric, thermal,drop-on-demand or continuous ink jet printing) or digital printing) thethird ink onto the second surface. In one embodiment, one or more dyesor pigments are included to the third ink and provide color to thesecond coating and ultimately formed feature. See Ernest W. Flick,Printing Ink and Overprint Varnish Formulations, Recent Developments(Noyes Publications 1991) (ISBN 0-8155-1259-7), and Ernest W. Flick,Printing Ink and Overprint Varnish Formulations, Second Edition (NoyesPublications 1999) (ISBN 0-8155-1440-9), the entireties of which areincorporated herein by reference, or an overview of various coatingformulations that may be employed for the third ink. The treating of thedeposited third ink preferably comprises drying, optionally with heatingand/or application of UV radiation to the deposited third ink. Somespecific preferred third ink compositions for forming the second coatinginclude RJE A8070 lacquer medium cvec12414 from Cavalier Inks andCoatings (Richmond, Va.); CK-49HG-1 and CK-1250 from Cork IndustriesInc. (Folcroft, Pa.); and NiCoat (noncurl 8020) from Gans Ink and SupplyCo. (Los Angeles, Calif.).

In one embodiment, at least one of the first surface or the secondsurface has an image disposed thereon. In this embodiment, at least aportion of the image preferably is viewable through the reflectiveelement when viewed at a first angle relative to the third surface, andat least a portion of the image is at least partially obscured whenviewed from a second angle relative to the third surface. The reflectiveelement formed by this process, therefore, at least partially obscuresthe image, depending on the viewing angle. Optionally, the second angleis about 180° minus the angle of incident light, relative to the thirdsurface. By way of non-limiting examples, the image may be formed from aprinting process selected from the group consisting of direct writeprinting, intaglio printing, gravure printing, lithographic printing,and flexographic printing. By way of non-limiting examples, the imagemay be selected from the group consisting of a black and white image, acolor image, a hologram, a watermark, a UV fluorescent image, text, anda serial number.

In another embodiment, the reflective element formed comprises aplurality of reflective images. In a related embodiment, the reflectiveelement formed comprises a plurality of reflective microimages, whereinthe plurality of reflective microimages has an average largest dimensionof less than about 0.5 mm. Optionally, at least one microimage comprisesvariable data.

In one aspect, the present invention relates to a reflective featurecomprising a substrate, a reflective element comprising metallicnanoparticles, and an overcoat comprising a colorant. The overcoatoptionally comprises a material selected from the group consisting of amaterial selected from the group consisting of a varnish, an offsetvarnish, a dry offset varnish, a shellac, latex, and a polymer. By wayof non-limiting examples, the colorant may be a dye or pigment. Theovercoat comprising the colorant may have the effect of changing thecolor of the reflective element and/or the substrate. For example, areflective element comprising metallic nanoparticles that appear silverin the absence of a colorant, may appear gold if the overcoat comprisesa colorant. In a preferred embodiment, the overcoat is transparent.Although a transparent overcoat allows light to pass through such thatthe reflective element remains visible, the overcoat still may createthe effect of changing the apparent color of the reflective element. Inaddition to affecting the apparent color of the reflective element, theovercoat may have the synergistic effect of protecting the reflectiveelement, and/or increasing the reflectivity of the reflective element.

In another aspect, the present invention relates to a process forforming a reflective feature, the process comprising the steps of:providing a substrate; forming a reflective element comprisingnanoparticles, preferably metallic nanoparticles, on the substrate; andforming an overcoat, optionally comprising a colorant, on the reflectiveelement. Optionally, the step of forming the reflective element,preferably comprising the metallic nanoparticles, comprises direct writeprinting an ink comprising the nanoparticles onto the substrate.Optionally, the step of forming the overcoat comprises direct writeprinting, e.g., ink jet printing, an ink, optionally comprising thecolorant, onto the substrate and/or the reflective element. Optionally,the overcoat comprising a colorant is transparent. The colorant employedin this process may be selected from virtually any pigment or dye thatis compatible with a direct write printing process.

EXAMPLES Example 1 Lacquer Undercoat to form Highly Reflective Feature

A multi-layer reflective feature comprising a substrate, an undercoatand a reflective feature was formed. The substrate comprised glossyEpson photopaper, which was made substantially non-porous by forming anon-porous lacquer undercoat on the surface of the paper. The coatingwas formed by applying RJE A8070 Lacquer Medium cvec 12414 (CavalierInks and Coatings, Richmond, Va.) onto the Epson photopaper and allowingit to dry.

An ink comprising silver nanoparticles (average particle size=20-80 nm)and rhodamine dye was ink jet printed onto the coated substrate. The inkwas ink jet printed onto the lacquer-coated paper utilizing aHewlett-Packard thermal ink jet printing head (Model HP45A cartridge)and allowed to dry. The printing pattern comprised a repeating patternof microprinted numbers (2 Pt. font size or smaller). The ink had theformulation shown in Table 1, below.

TABLE 1 SILVER NANOPARTICLE/RHODAMINE INK JET INK FORMULATION IngredientWeight Percent Rhodamine 4.3 Silver Nanoparticles 9.5 Glycerol 16.4Ethanol 44.0 Ethylene Glycol 25.8

Visibly, the feature was surprisingly reflective and unexpectedlyexhibited a color shift between a dark red metallic color and a greenmetallic color as the viewing angle changed.

Example 2 Lacquer Undercoat to form Highly Reflective Feature

A multi-layer reflective feature comprising a substrate, an undercoatand a reflective feature was formed. The substrate comprised glossyEpson photopaper, which was made substantially non-porous by forming anon-porous lacquer undercoat on the surface of the paper. The coatingwas formed by applying RJE A8070 Lacquer Medium cvec 12414 (CavalierInks and Coatings, Richmond, Va.) onto the Epson photopaper and allowingit to dry.

An ink comprising silver nanoparticles (average particle size=20-80 nm)and basic fuchsin dye was ink jet printed onto the coated substrate. Theink was ink jet printed onto the lacquer-coated paper utilizing aHewlett-Packard thermal ink jet printing head (Model HP45A cartridge)and allowed to dry. The printing pattern comprised a repeating patternof microprinted numbers (2 Pt. font size or smaller). The ink had theformulation shown in Table 2, below.

TABLE 2 SILVER NANOPARTICLE/BASIC FUCHSIN INK JET INK FORMULATIONIngredient Weight Percent Basic Fuchsin 4.3 Silver Nanoparticles 9.5Glycerol 16.4 Ethanol 44.0 Ethylene Glycol 25.8

Visibly, the feature was surprisingly reflective and unexpectedlyexhibited a color shift between a dark red metallic color and a greenmetallic color as the viewing angle changed.

Example 3 Lacquer Overcoat to Form Durable Reflective Feature

A reflective feature was formed by ink jet printing an ink comprisingsilver nanoparticles (average particle size=20-80 nm) and treating thefirst layer to form a first coating, and then forming a second layercomprising a colored lacquer on top of the first layer. The substratecomprised (uncoated) glossy Epson photopaper.

The ink had the formulation shown in Table 3, below.

TABLE 3 SILVER NANOPARTICLE INK JET INK FORMULATION Ingredient WeightPercent Silver Nanoparticles 10.0 Glycerol 17.0 Ethanol 46.0 EthyleneGlycol 27.0

The ink was deposited on the substrate utilizing a Hewlett-Packardthermal ink jet printing head (Model HP45A cartridge) and allowed todry. The printing pattern comprised a repeating pattern of microprintednumbers (2 Pt. font size). After drying, a colored lacquer coating wasdeposited on the surface of the paper with a draw bar and allowed todry. The colored coating was formed by adding rhodamine dye to RJE A8070Lacquer Medium cvec 12414 (Cavalier Inks and Coatings, Richmond, Va.) toobtain a 5 wt % rhodamine concentration, based on the total weight ofthe colored lacquer coating. The reflective feature formed in Example 3thus had two layers, a first silver nanoparticle layer, and a coloredlacquer overcoat disposed thereon. The feature was surprisinglyreflective and appeared to have a lustrous red metallic color. Thefeature was also surprisingly durable, exhibiting a rating of 5 on theASTM D-5264D92 rub test.

While the present invention has been described with reference toexemplary embodiments, it is understood that the words that have beenused are words of description and illustration, rather than words oflimitation. Changes may be made, within the purview of the appendedclaims, as presently stated and as amended, without departing from thescope and spirit of the present invention in its aspects. Although theinvention has been described herein with reference to particular means,materials, and embodiments, the invention is not intended to be limitedto the particulars disclosed herein. Instead, the invention extends toall functionally equivalent structures, methods, and uses, such as arewithin the scope of the appended claims.

1. A reflective feature, comprising: (a) a substrate having a firstregion and a second region, the first and second regions havingdifferent surface characteristics; (b) a first reflective elementdisposed on the first region; and (c) a second reflective elementdisposed on the second region, wherein the first reflective element ismore adherent than the second reflective element to the first region. 2.The reflective feature of claim 1, wherein the second reflective elementis more adherent than the first reflective element to the second region.3. The reflective feature of claim 1, wherein the first reflectiveelement is disposed exclusively on the first region.
 4. The reflectivefeature of claim 1, the substrate further comprising a third region, thereflective feature further comprising a third reflective elementdisposed on the third region, wherein the third reflective element ismore adherent than the first reflective element or the second reflectiveelement to the third region.
 5. The reflective feature of claim 1,wherein the first reflective element comprises metallic nanoparticles.6. The reflective feature of claim 5, wherein the second reflectiveelement comprises metallic nanoparticles.
 7. The reflective feature ofclaim 1, wherein the first region comprises a composition selected fromthe group consisting of foil, film, UV-coated lacquer, paper, coatedpaper, polymer, and printed paper.
 8. The reflective feature of claim 1,wherein the second region comprises a composition selected from thegroup consisting of foil, film, UV-coated lacquer, paper, coated paper,and printed paper.
 9. The reflective feature of claim 1, wherein thefirst reflective element and the second reflective element form acontinuous graphical feature that spans at least a part of the firstregion and at least a part of the second region.
 10. The reflectivefeature of claim 1, wherein at least one of the first reflective elementand/or the second reflective element comprises variable information. 11.The reflective feature of claim 1, wherein the substrate is selectedfrom the group consisting of a banknote, a brand authentication tag, atax stamp, an ID document, an alcoholic bottle, and a tobacco product.12. The reflective feature of claim 1, wherein the first regioncomprises a first undercoat.
 13. The reflective feature of claim 12,wherein the first reflective element exhibits enhanced reflectivityrelative to the reflectivity of the first reflective element on thefirst region in the absence of the first undercoat.
 14. The reflectivefeature of claim 12, wherein the second region comprises a secondundercoat.
 15. The reflective feature of claim 13, wherein the secondreflective element exhibits enhanced reflectivity relative to thereflectivity of the second reflective element on the second region inthe absence of the second undercoat.
 16. The reflective feature of claim1, further comprising a first overcoat disposed on the first reflectiveelement.
 17. The reflective feature of claim 16, wherein the firstreflective element exhibits enhanced reflectivity relative to thereflectivity of the first reflective element without the first overcoat.18. The reflective feature of claim 16, wherein the first reflectiveelement exhibits enhanced durability relative to the durability of thefirst reflective element without the first overcoat.
 19. The reflectivefeature of claim 16, wherein the first overcoat is further disposed onthe second reflective element.
 20. The reflective feature of claim 19,wherein the second reflective element exhibits enhanced reflectivityrelative to the reflectivity of the second reflective element withoutthe first overcoat.
 21. The reflective feature of claim 19, wherein thesecond reflective element exhibits enhanced durability relative to thedurability of the second reflective element without the first overcoat.22. The reflective feature of claim 16, further comprising a secondovercoat disposed on the second reflective element.
 23. The reflectivefeature of claim 22, wherein the second reflective element exhibitsenhanced reflectivity relative to the reflectivity of the secondreflective element without the second overcoat.
 24. The reflectivefeature of claim 22, wherein the second reflective element exhibitsenhanced durability relative to the durability of the second reflectiveelement without the second overcoat.
 25. The reflective feature of claim1, wherein the first region is more porous than the second region. 26.The reflective feature of claim 1, wherein the first region is morehydrophobic than the second region.
 27. A process for forming areflective feature, the process comprising the steps of: (a) providing asubstrate comprising a first region and a second region; (b) directwrite printing a first ink onto the first region to form a firstreflective element; and (c) direct write printing a second ink onto thesecond region to form a second reflective element, wherein the first inkis more adherent than the second ink to the first region.
 28. Theprocess of claim 27, wherein the second ink is more adherent than thefirst ink to the second region.
 29. The process of claim 27, furthercomprising the step of direct write printing a third ink onto a thirdsubstrate surface to form a third reflective element, wherein thesubstrate further comprises the third substrate surface, and wherein thethird ink is more adherent than the first ink or the second ink to thethird region.
 30. The process of claim 27, wherein at least one of thefirst ink and the second ink comprises metallic nanoparticles.
 31. Theprocess of claim 27, wherein the first region comprises a compositionselected from the group consisting of foil, film, UV-coated lacquer,paper, polymer, coated paper, and printed paper.
 32. The process ofclaim 31, wherein the second region comprises a composition selectedfrom the group consisting of foil, film, UV-coated lacquer, paper,coated paper, and printed paper.
 33. The process of claim 27, whereinthe first reflective element and the second reflective element form acontinuous graphical feature that spans at least a part of the firstregion and at least a part of the second region.
 34. The process ofclaim 27, wherein at least one of the first reflective element and thesecond reflective element comprises variable information.
 35. Theprocess of claim 27, wherein the substrate is selected from the groupconsisting of a banknote, a brand authentication tag, a tax stamp, an IDdocument, an alcoholic bottle, and a tobacco product.
 36. The process ofclaim 27, wherein the first region comprises a first undercoat.
 37. Theprocess of claim 36, wherein the first reflective element exhibitsenhanced reflectivity relative to the reflectivity of the firstreflective element on the first region in the absence of the firstundercoat.
 38. The process of claim 36, wherein the second regioncomprises a second undercoat.
 39. The process of claim 38, wherein thesecond reflective element exhibits enhanced reflectivity relative to thereflectivity of the second reflective element on the second region inthe absence of the second undercoat.
 40. The process of claim 27,wherein a first overcoat is formed on the first reflective element. 41.The process of claim 40, wherein the first reflective element exhibitsenhanced reflectivity relative to the reflectivity of the firstreflective element without the first overcoat.
 42. The process of claim40, wherein the first reflective element exhibits enhanced durabilityrelative to the durability of the first reflective element without thefirst overcoat.
 43. The process of claim 40, wherein the first overcoatis further formed on the second reflective element.
 44. The process ofclaim 43, wherein the second reflective element exhibits enhancedreflectivity relative to the reflectivity of the second reflectiveelement without the first overcoat.
 45. The process of claim 43, whereinthe second reflective element exhibits enhanced durability relative tothe durability of the second reflective element without the firstovercoat.
 46. The process of claim 40, wherein a second overcoat isformed on the second reflective element.
 47. The process of claim 46,wherein the second reflective element exhibits enhanced reflectivityrelative to the reflectivity of the second reflective element withoutthe second overcoat.
 48. The process of claim 46, wherein the secondreflective element exhibits enhanced durability relative to thedurability of the second reflective element without the second overcoat.49. The process of claim 27, wherein the first region is more porousthan the second region.
 50. The process of claim 27, wherein the firstregion is more hydrophobic than the second region.
 51. A reflectivefeature, comprising: (a) a substrate having a first surface; (b) a firstcoating disposed on the first surface and having a second surface; and(c) a reflective element having a third surface and comprisingnanoparticles disposed, at least in part, on the second surface.
 52. Thereflective feature of claim 51, wherein the first surface comprises tworegions having different surface characteristics, and the first coatingcovers at least a portion of both regions.
 53. The reflective feature ofclaim 52, wherein the reflective element covers at least a portion ofthe two regions.
 54. The reflective feature of claim 51, wherein thefirst coating comprises a material selected from the group consisting ofvarnishes, offset varnishes, dry offset varnishes, shellacs, andpolymers.
 55. The reflective feature of claim 51, wherein the firstcoating comprises a colorant.
 56. The reflective feature of claim 51,the reflective feature further comprising: (d) a second coating having afourth surface disposed, at least in part, on the third surface.
 57. Thereflective feature of claim 56, wherein the second coating istransparent.
 58. The reflective feature of claim 56, wherein the secondcoating comprises a material selected from the group consisting of: avarnish, an offset varnish, a dry offset varnish, a shellac, latex, anda polymer.
 59. The reflective feature of claim 51, wherein thenanoparticles comprise phosphorescent nanoparticles.
 60. The reflectivefeature of claim 51, wherein the nanoparticles comprise metallicnanoparticles.
 61. The reflective feature of claim 60, wherein amajority of the metallic nanoparticles are necked with at least oneadjacent metallic nanoparticle.
 62. The reflective feature of claim 60,wherein the metallic nanoparticles comprise a metal selected from thegroup consisting of silver, gold, zinc, tin, copper, platinum andpalladium, and alloys thereof.
 63. The reflective feature of claim 60,wherein the metallic nanoparticles have an average particle size of lessthan about 200 nm.
 64. The reflective feature of claim 60, wherein themetallic nanoparticles have an average particle size of from about 50 nmto about 100 nm.
 65. The reflective feature of claim 60, wherein thereflective element comprises a reflective layer that is at leastpartially semitransparent.
 66. The reflective feature of claim 60,wherein the reflective element comprises a continuous reflective layer.67. The reflective feature of claim 60, wherein the reflective elementcomprises a non-continuous reflective layer.
 68. The reflective featureof claim 60, wherein the reflective feature is more reflective than itwould be in the absence of the first coating.
 69. The reflective featureof claim 60, wherein at least one of the first surface or the secondsurface has an image disposed thereon, and wherein at least a portion ofthe image is viewable through the reflective element when viewed at afirst angle relative to the third surface, and wherein the at least aportion of the image is at least partially obscured when viewed from asecond angle relative to the third surface.
 70. The reflective featureof claim 69, wherein the second angle is about 180° minus the angle ofincident light, relative to the third surface.
 71. The reflectivefeature of claim 69, wherein the image is formed from a printing processselected from the group consisting of direct write printing, intaglioprinting, gravure printing, lithographic printing and flexographicprinting processes.
 72. The reflective feature of claim 69, wherein theimage is selected from the group consisting of a hologram, a black andwhite image, a color image, a watermark, a UV fluorescent image, textand a serial number.
 73. The reflective feature of claim 60, wherein thereflective element comprises a plurality of reflective images.
 74. Thereflective feature of claim 60, wherein the reflective element comprisesa plurality of reflective microimages, wherein the plurality ofreflective microimages has an average largest dimension of less thanabout 0.5 mm.
 75. The reflective feature of claim 74, wherein at leastone microimage comprises variable data.
 76. A process for forming areflective feature, the process comprising the steps of: (a) providing asubstrate having a first surface; (b) forming a first coating on thefirst surface, the first coating having a second surface; and (c)forming a reflective element on the second surface, the reflectiveelement having a third surface and comprising nanoparticles.
 77. Theprocess of claim 76, wherein the first surface comprises two regionshaving different surface characteristics, and the first coating coversat least a portion of both regions.
 78. The process of claim 77, whereinthe reflective element covers at least a portion of the two regions. 79.The process of claim 76, wherein step (b) comprises depositing a firstink onto the first surface and treating the deposited first ink underconditions effective to form the first coating.
 80. The process of claim79, wherein the depositing comprises direct write printing the first inkonto the first surface.
 81. The process of claim 79, wherein thetreating comprises heating the deposited first ink.
 82. The process ofclaim 79, wherein the treating comprises applying UV radiation to thedeposited first ink.
 83. The process of claim 76, wherein step (c)comprises depositing a second ink onto the second surface and treatingthe deposited second ink under conditions effective to form thereflective element.
 84. The process of claim 83, wherein the depositingcomprises direct write printing the second ink onto the second surface.85. The process of claim 83, wherein the treating comprises heating thedeposited second ink.
 86. The process of claim 83, wherein the treatingcomprises applying UV radiation to the deposited second ink.
 87. Theprocess of claim 76, wherein the first coating comprises a materialselected from the group consisting of: a varnish, an offset varnish, adry offset varnish, a shellac, latex, and a polymer.
 88. The process ofclaim 76, the process further comprising the step of: (d) forming asecond coating on the third surface, the second coating having a fourthsurface.
 89. The process of claim 88, wherein the second coating istransparent.
 90. The process of claim 88, wherein the second coatingcomprises a material selected from the group consisting of: a varnish,an offset varnish, a dry offset varnish, a shellac, latex, and apolymer.
 91. The process of claim 76, wherein the nanoparticles comprisephosphorescent nanoparticles.
 92. The process of claim 76, wherein thenanoparticles comprise metallic nanoparticles.
 93. The process of claim92, wherein a majority of the metallic nanoparticles are necked with atleast one adjacent metallic nanoparticle.
 94. The process of claim 92,wherein the metallic nanoparticles comprise a metal selected from thegroup consisting of silver, gold, zinc, tin, copper, platinum andpalladium, and alloys thereof.
 95. The process of claim 92, wherein themetallic nanoparticles have an average particle size of less than about200 nm.
 96. The process of claim 92, wherein the metallic nanoparticleshave an average particle size of from about 50 nm to about 100 nm. 97.The process of claim 92, wherein the reflective element comprises areflective layer that is at least partially semitransparent.
 98. Theprocess of claim 92, wherein the reflective element comprises acontinuous reflective layer.
 99. The process of claim 92, wherein thereflective element comprises a non-continuous reflective layer.
 100. Theprocess of claim 92, wherein the reflective feature is more reflectivethan it would be in the absence of the first coating.
 101. The processof claim 92, wherein at least one of the first surface or the secondsurface has an image disposed thereon, wherein at least a portion of theimage is viewable through the reflective element when viewed at a firstangle relative to the third surface, and wherein the at least a portionof the image is at least partially obscured when viewed from a secondangle relative to the third surface.
 102. The process of claim 101,wherein the second angle is about 180° minus the angle of incidentlight, relative to the third surface.
 103. The process of claim 101,wherein the image is formed from a printing process selected from thegroup consisting of direct write printing, intaglio printing, gravureprinting, lithographic printing and flexographic printing processes.104. The process of claim 101, wherein the image is selected from thegroup consisting of a hologram, a black and white image, a color image,a watermark, a UV fluorescent image, text and a serial number.
 105. Theprocess of claim 92, wherein the reflective element comprises aplurality of reflective images.
 106. The process of claim 92, whereinthe reflective element comprises a plurality of reflective microimages,wherein the plurality of reflective microimages has an average largestdimension of less than about 0.5 mm.
 107. The process of claim 106,wherein at least one microimage comprises variable data.
 108. Areflective feature, comprising (a) a substrate; (b) a reflective elementcomprising metallic nanoparticles; and (c) an overcoat comprising acolorant.
 109. The reflective feature of claim 108, wherein the overcoatis transparent.
 110. The reflective feature of claim 108, wherein theovercoat comprises a material selected from the group consisting of: avarnish, an offset varnish, a dry offset varnish, a shellac, latex, anda polymer.
 111. A process for forming a reflective feature, the processcomprising the steps of: (a) providing a substrate; (b) forming areflective element on the substrate, the reflective element comprisingmetallic nanoparticles; and (c) forming an overcoat on the reflectiveelement, the overcoat comprising a colorant.
 112. The process of claim111, wherein the step of forming the reflective element comprisingmetallic nanoparticles comprises direct write printing an ink comprisingthe metallic nanoparticles onto the substrate.
 113. The process of claim111, wherein the step of forming the overcoat comprising a colorantcomprises direct write printing an ink comprising the colorant onto thesubstrate and/or the reflective element.
 114. The process of claim 111,wherein the overcoat is transparent.